#include <stdio.h>

int main(void)
{
    double water_quarts;
    // quality of single water molecule: 3.0e-23 gram
    double h2o = 3.0e-23;
    // quality of 1 quart of water: 950 gram
    double water_quart = 950.0;

    printf("How many quarts of water? ");
    scanf("%lf", &water_quarts);
    printf("%.2lf quart(s) of water has %.0lf water molecules.\n", water_quarts, water_quarts * water_quart / h2o);

    return 0;
}